The present invention relates to an ultrasonic sound wave generating device and, in particular, to such a device especially adapted for repelling animals.
Devices for generating ultrasonic sound waves which are inaudible to man but within the audible range of many kinds of animals are well known. Typically, these devices are employed for the purpose of repelling pest animals such as insects, birds, small mammals such as mice, bats, rats, etc., from a particular site, for example, a place where foodstuffs are grown or stored, and from discouraging them from intruding upon, gaining access to, or occupying the site. Illustrative of such devices are those disclosed in U.S. Pat. Nos. 2,922,999; 3,138,138; 3,188,999; 3,277,861; 3,522,791; and 4,284,845, the contents of which are incorporated by reference herein.
Devices for the detection of a moving human intruder which remote-senses the infra-red radiation emitted by the intruder when the intruder has come within the infra-red radiation-sensing range of the devices are also known. Several of these devices feature means for activating an alarm which is audible to the human ear when the infra-red radiation detector has sensed the presence of an intruder. Illustrative of such devices are those disclosed in U.S. Pat. Nos. 3,760,399; 3,792,275; 4,087,688; and, 4,271,358, the contents of which are incorporated by reference herein.
Another remote sensing device which operates upon an entirely different detection principle is the carbon dioxide measurement apparatus of U.S. Pat. No. 3,963,927 the contents of which are incorporated herein. While the device is primarily designed to detect hidden insects, with appropriate modification, it could also be used to detect larger animals from a distance.
Devices which trigger a signal or switch upon sensing a disturbance are also known. Thus the gravity switching device of U.S. Pat. No. 3,599,745, the contents of which are incorporated by reference herein, can sense when a tractor or other machine is tilted to an unsafe operating position whereupon a switch will interrupt the flow of fuel to the engine or cut off the ignition. U.S. Pat. No. 4,434,337, the contents of which are also incorporated by reference herein describes a mercury switch which is activated by a tilting movement.
None of the foregoing patents disclose or suggest an animal-repelling ultrasonic sound wave generating device which is temporarily activated when a detector, for example, an infra-red radiation detector, has sensed the presence of an animal intruder within its vicinity.